Ceiling HVAC ductswork problem

[ixlar8]

I have a Silvercrest 1987 manufactured home on permanent foundation. The HVAC is an up flow with all the feeding flexible ducts in the ceiling. There is no ductwork for air return except a central return.
One half of the house has no airflow, and has cathedral ceilings with no access. I can access the ceiling near the furnace and the half of the house with the good airflow and this ductwork appears to be okay.
However, two ducts from the furnace feed into the other half which is a sealed ceiling and I cannot see into this part.
I suspect that some of the flexible ductwork has separated and is venting air into the attic space, but it is inaccessible except to cut into the ceiling drywall.
Before I do this, is there another central duct box with the flexible ductwork in this part of the house ceiling? If so, is this the most likely spot to start cutting into the ceiling? I do not want to spend the day slicing holes all over my ceiling to find the bad duct if I can centralize a location.

[David Oxhandler]

The crossover duct work can be located above the ceiling or below or even in the floor ... depending on the year make and model of the home. Give us those details and one of the regulars here may be able to offer you some guidance.